books.google.co.nz - From a comparative perspective, human life histories are unique and raising offspring is unusually costly: humans have relatively short birth intervals compared to other apes, childhood is long, mothers care simultaneously for many dependent children (other apes raise one offspring at a time), infant...https://books.google.co.nz/books/about/Substitute_Parents.html?id=-f7rwzVqYUkC&utm_source=gb-gplus-shareSubstitute Parents